hand disinfectants

Hand sanitizers became something almost impossible to avoid. Most ladies carry a bottle in their purse, it’s in pretty much every bathroom, and it oftentimes acts as a substitute for washing hands. Although they are so often used, many people don't know exactly what they are and what they do. Are hand sanitizers a substitute for washing your hands? Do they work? Do they say what they mean on the bottle? Do many of them, as they claim, kill 99% of all germs? Does it kill only the bad germs? Is it tough for your hands?